Treatment of tapioca starch wastewater by a novel combination of physical and biological processes.

A pilot plant combining dissolved air flotation, anaerobic degradation in an expanded granular sludge bed (EGSB) reactor and aerobic post-treatment in a vertical flow constructed wetland has been used to treat tapioca starch wastewater for more than 2.25 years. It is demonstrated that organic matter (chemical oxygen demand by >98%), nitrogen (Kjeldahl-N by >90%) and cyanide (total cyanide by >99%) can be removed very efficiently under stable operating conditions. The removal efficiency for phosphorus is lower (total-P by 50%). The treatment concept, which includes several sustainable aspects, e.g. production of energy to be used on-site, low operation demands and minimal use of chemicals, could be interesting for small- and middle-sized tapioca processing plants.